1. Field of the Invention
This invention relates to a thermal processing unit that can conduct a thermal process to an object to be processed.
2. Disclosure of the Prior Art
In manufacturing semiconductor devices, various types of thermal processing units are used for conducting a process such as oxidation, diffusion or CVD (Chemical Vapor Deposition) to an object to be processed such as a wafer. As one of them, a vertical thermal processing unit is known, which can conduct a thermal process to a large number of objects to be processed at a time. The vertical thermal processing unit has a vertical cylindrical processing container made of crystal. An upper end of the processing container is closed, but a lower end of the processing container is open as a furnace opening. A flange is provided at a peripheral portion of the furnace opening. A heater is disposed to surround the processing container.
If the unit is designed for a diffusion process, it should be considered that a process temperature is high. That is, taking a heat-resistance property into consideration, a gas-supplying unit (a gas-supplying port) consisting of a crystal tube is provided at a lower side portion of the processing unit (higher than the flange) in order to introduce a gas such as a process gas into the processing unit.
If the unit is designed for a CVD process, a manifold made of a metal is joined to the lower open end of the processing unit. In addition, a gas-supplying unit consisting of a metal tube is provided at a side portion of the manifold.
The lower open end of the processing container or a lower open end of the manifold is adapted to be opened and hermetically closed by a lid. A holding tool (a holding boat), which can hold a large number of wafers, for example 150 wafers, in a vertical tier-like manner at a predetermined pitch, is placed on the lid via a thermal insulating cylinder that is a furnace-opening insulating means. A loading area is arranged under the processing container for loading and unloading the holding tool. An elevating mechanism is disposed in the loading area for loading and unloading the holding tool into and from the processing container by moving up and down the lid.
However, in the above vertical thermal processing unit, under the processing container, a space has to be secured for arranging the loading area and the elevating mechanism. In addition, at a lower side portion of the processing container, a space has to be secured for disposing the gas-supplying unit (or the manifold if the unit is designed for the CVD process). Thus, the unit has a greater height undesirably.
Especially, if the loading area is designed for a load-lock type, a structure for maintaining a vacuum needs more height. If the wafer-pitch is reduced because of restriction of the height of the unit, it may become difficult to obtain a film having a desired property.
If the unit is designed for a diffusion process, the gas-supplying unit (the gas-supplying port) consisting of the crystal tube is provided to project from the side portion of the processing unit. Thus, the gas-supplying unit may be easily damaged by an outer force or an impact, that is, it may be weak in strength.
If the unit is designed for a CVD process, the gas-supplying unit has no problems in strength because the manifold made of a metal is used. However, in the case, it is necessary to cool a sealing portion in order to prevent an O-ring as a sealing member from thermally deteriorating. In addition, it is necessary to prevent separation (deposition) of the process gas, which may be caused by the cooling of the sealing portion, by way of heating or the like. These result in a complex structure.
This invention is intended to solve the above problems effectively. An object of this invention is to provide a thermal processing unit wherein a height of the unit may be considerably reduced, strength of a gas-supplying unit may be enhanced, a structure of a processing container may be simplified, and process performance may be improved.
This invention is a thermal processing unit comprising: a processing container that can contain an object to be processed therein, the processing container having a lower end provided with an opening; a lid that can open and close the opening; a flange provided at a peripheral portion of the opening; a gas-supplying unit provided at the flange for supplying a gas into the processing container; and a heating mechanism that can heat the object to be processed contained in the processing container.
According to the feature, since the gas-supplying unit is provided at the flange itself, a height of the unit may be considerably reduced, strength of the gas-supplying unit may be enhanced, a structure of the processing container may be simplified and process performance of the unit may be improved.
Preferably, the gas-supplying unit has a gas-supplying hole that extends from an outer edge of the flange to an inside of the processing container.
For example, the processing container has a substantially cylindrical shape, the flange has a substantially circular shape, and the gas-supplying hole extends in a substantially radial direction of the flange.
Preferably, a gas-supplying tube is inserted through the gas-supplying hole to extend into the processing container. Thus, a process gas is efficiently supplied into the processing container. In the case, preferably, the flange is provided with a fixing mechanism that can fix the gas-supplying tube to the flange.
In addition, preferably, the gas-supplying tube is hermetically connected with a gas-supplying line. In the case, the gas-supplying line may be connected easily and desirably.
In addition, preferably, a circular supporting frame is provided at a peripheral area of the flange. In the case, strength of the flange and the gas-supplying unit may be enhanced. For example, the circular supporting frame is made of a metal.
Alternatively, preferably, a circular supporting frame is provided at a peripheral area of the flange, the circular supporting frame has a through hole that extends from an inter edge to an outer edge thereof, and the through hole is communicated with the gas-supplying hole. In the case too, for example, the circular supporting frame is made of a metal.
Alternatively, preferably, a circular supporting frame is provided at a peripheral area of the flange, the circular supporting frame has a through hole that extends from an inter edge to an outer edge thereof, and the gas-supplying tube passes through the through hole. In the case too, for example, the circular supporting frame is made of a metal. In the case, the circular supporting frame is preferably provided with a fixing mechanism that can fix the gas-supplying tube to the circular supporting frame.